Thermal relay and cut-out



Oct. 13I 1925- N. K ANDERSEN THERMAL RELAY AND CUI`-OUT Filed Sept. ll 1921 13M a' y 1114 INVENTOR lififf BY ATTORNEY WITNESSES; WW

Patented Oct. 13, `1925.

UNITED STATES PATENT OFFICE.

NIELS K. .ANDERSEN, OF W'ILKINSBURGy. EENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRC &, MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

Application filed September 1, 1921.

To all whom t may conce/"n:

Be it known that l, Nrmis K. ANnnnsEN,

a subject ot' the King of Denmark, and a resident ot lYilltins-l'iurg. in the county of Allegheny and State of Pennsylvania, have invented anew and useful Improvement in Thermal Relays and Cut-Outs of which the following is a speciiication.

My invention relates to relays and particularly to thermal relays and cutouts.

One object `of my invention is to provide a thermal relay or cutout comprising a thermal elementl that has a negative coetlicient of expansion.

Another object of my invention is to provide a protective device, of the above-indicated character, in which the thermaltele-y ment decreases in volume at its fusing tem perature.

Another object of my invention is to provide a protective device, of the above-indicated character, in which the. thermal element ruptures an electric circuit.

A further object of my invention is to provide a protective device, of the aboveindicated character, that may be readily inserted in iuseterminal. clips otl standard type, and that shall be relatively simple and inexpensive in construction and reliable in operation.

In practicing my invention, l provide a tubular member of insulating material containing a conducting material, such as bis-I Inuth, which decreases in voluuie at its fusing temperature. The tubular` member is enclosed in a casing ol" non-conducting material, such as is ordinarily employed with standardfuses, to retain the heatV from the current-heated bismuth. Metallic ferrul'es, disposed at each end of the casing and electrically connected to the bismuth, provide means whereby the relay may be readily inserted into an electrical circuit.

Fivure 1- of the accompanying drawings is-a diagrammatic view of an electrical cir cuit containing a device embodying my invention, and Y Fig. 2 is a diagran'nnatic view of an electrical circuit containing a modified form of protective device embodying my invention.

ln Fig. 1, a motor 1 receives'energy from a source Q of electromotive torce and is controlled by a protective device 3.

r n lhe protective device comprises a. tubu- THERMAL RELAY AND our-OUT.

Serial No. 497,476.

lar member il containing a conducting material 5, such as bismuth, that is adapted to decrease in volume at its fusing temperature. The protective device further comprises an enclosing casing 6 and end ferrules 7 and 8.

The tubular member it comprises a capillary tube 9, two end bulbs 10 'and 11, an auxiliarj.' bulb 12 that. is disposed inter mediate the end bulbs 10 and 11, and a plurality of terminal members 18 and 14 that are respectively disposed in the bulbs 10 and 1l. The terminal members 13 and 14C are soldered to the end ferrules 7 and 8. The portion of the capillary tube 9 adjacent the bulb 12 is slightly constricted.

The portion of the' tubular member 4 between the terminal members 13 and 111 is filled with bismuth or other suitable material. and the auxiliary bulb 12 contains a non-conducting fluid, such as air or other gas. As current traverses the motor and the protective device 3, the bismuth 5 becomes heatedin accordance With the value of such current and attains a temperature corresponding substantially to the tempera tui-cof themotor 1. Undue dissipation ot' heat from the. heated bismuth is precluded by the enclosing member 6, andthe temperature Within the protective device 3 thus tends to correspond to substantially the temperature Within the motor 1.

As the temperature of the bismuth increases, the temperature of the` iuid within the auxiliary bulb correspondingly increases, and, as the portion of the bismuth opposite the bulb 12 begins to fuse, because of the relatively greater resistance at that part ot the tube, the increased pressure of the Huid within the bulb 12 tends to decrease. the` cross-sectional area of the bisninth at. that point. The resistance of the bismuth is thus increased at that portion of the path and the heating becomes so concentrated that the bismuth fuses more rapidly at this portion until the cross-sectional area. becomes furtherdecreased and the continuity of the bismuth column is finally broken.l

'lhe motor l is thus protected from overheating and, until the bismuth column is re established, the motor cannot be reconnected to the circuit 2.

The device shown in Fig. 1 is applicable Ulti' to motors having a small current-carrying capacity of such value as may be directly' interrupted by a cutout of the type vthat is described.

In Fig. 2 is illustrated a relay of the' type that is 'employed for the protection of electrical -apparatus of large current-carrying capacity. The motor 1 receives energy from a source 2 of electromotive forcethrough a circuit interrupter 20, the operation of which is controlled by. means o a thermal relay 21.

The interrupter 20 isI provided with a holding coil 22 that maintains the interrupter closed against the tension of a spring 23 Whilev the coil is energized. Upon the deenergization of the coil 92 the interrupter -2, is opened by the spring The circuit of the holding coil 22 is controlled by the`I thermal relay 21, being opened thereby upon the occurrence of abnormal heating conditions Within the motor 1.

The relay 21 comprises elements similar to those of the relay 3 shown in F ig. 1, andin addition thereto, an auxiliary capillary tube and bulb portion 24 containing a smaller thread of bismuth and a terminal member 25 that is disposed therein.

As the temperature of the bismuth in the tubular member 9 and, consequently, in the auxiliary portion r24 attains a predetermined value, the fluid Within 'the auxiliary bulb 12 acts upon .the small-thread portion of bismuthA Within the auxiliary portion 2-1 and interrupts the continuity of that portion in a manner similar to that described above in connect-ion -with the device shown in Fig. 1'. The circuit of the, holding coil 22 is thereupon interrupted and the interrnpter permitted to open.

When the bismuth re-solidities, the circuit between the contact members-25 and 13 and 14 is re-established and;4 the holding coil 22 may be rie-energized by means of a pushbutton switch 2G to eliect the re-closing oit' the interrupter 20. When the interruptor 20 is reclosed, the circuit of' the holding coil is re-established through the contact members of the interrupter 20, and the pushbutton switch 26 may be released.

My invention is not limited to the Specific arrangement ot' the apparatus that is illustrated in the acconnianying drawings but may be variously modified within the spirit and scope of my invention, as sel 'lorth in the appended claims.

I claim as my invention:

1. A thermal relay comprising a closed receptacle containing a conducting material that decreases in volume at its fusing point and means responsive to the temperature thereof for controlling the conductivity of a portion of the material.

2. A receptacle for a therrnril-responsive that are,

element ot a thermal relay comprising a tubnlar` member embodying a bulb at each end thereof and an auxiliary bulbous portion intermediate the ends olf the tubular member and communicating with the opening through the tubular member, and terminal members in each bulb le be connected to an external circuit.

3. A thermal relay comprising a tubular container, an electrically conducting heatresponsive material therein, terminal members arranged to include the Whole length of the material in circuit therewith and an auxiliary terminal member communicating with the heat-responsive material at a point intermediate the aore-mentioned terminal members.

4. A self-resetting thermal protective device for an electric circuit comprising an element heated in accordancewith the current traversing the circuit andmeans in direct contact With-and directly thermally controlled by said element to cause they element to open a predetermined circuit.

5. A thermal relay comprising a closed receptacle containing a conducting material` that decreases in volume at its fusing point` and means associated withI said conducting material for causing said decrease iirvolume to be eli'ectcd at a predetermined portion olf said conducting material.

(3. A thermal relay comprising a closed receptacle of electric-insu]ating .material and containing an electric-conducting mav terial that decreases in volume at its 'fusing peint, and means operatively associated with said electric-conducting material and responsircto the ten'iperature thereof foi' causing said decrease in volume to be elleeted at a predetermined portion of said conducting material.

7. A self-resetting thermal protective device for an electric circuit comprising an elongated element that decreases in volume at its fusing point and that is heated in aecordance with the current traversing the circuit, and means associated with said element and directly heated thereby to ell'ect fusion thereot` at a predetermined point only whereby to open ai, predetermined circuit.

8. A self-resetting thermal protective device fer an electric circuit con'iprising an elongated current-conducting element `that decreases in volume al ils fusing oint, and means associated therewith and directly heated thereby to ellect 'fusion thereof at a predetermined point only to cause the elementA to open a predetermined circuit.

ln testimony u'hereol'. l have hereunto subscribed my name this irst day ot August v192i.

NIELS K. .aXNDlil {Sli/W. 

